1. Preheat oven to 375°F (190°C) and grease a 9×13-inch casserole dish.

2. In a large skillet, melt 2 tablespoons butter over medium heat. Add sliced squash and diced onion; sauté until tender, about 5–7 minutes.

3. Drain excess liquid from the cooked squash and transfer to a mixing bowl.

4. In a separate bowl, whisk together eggs, heavy cream, salt, pepper, and garlic powder.

5. Stir shredded cheddar cheese into the egg and cream mixture.

6. Pour the egg–cream–cheese mixture over the drained squash and onions; mix gently to combine.

7. Spread the squash mixture evenly in the prepared casserole dish.

8. In a small bowl, combine breadcrumbs (or crushed crackers) with 2 tablespoons melted butter; sprinkle over the top of the casserole.

9. Bake uncovered for 25–30 minutes, or until the casserole is bubbly and the topping is golden brown.

10. Allow to rest for 5 minutes before serving to set.

11. Serve warm as a main dish or side alongside roast chicken, pork, or a green salad.